While PSE provides a good approximation of the overall behaviour of wavepackets in turbulent jets at low computational cost, it also has several limitations, such as its inability to predict the wavepacket characteristics at low frequencies [1]}. This problem is addressed if more advanced methods, like resolvent analysis [2]}, are employed. As shown by [3]}, response modes predicted by resolvent analysis are closely related to the most energetic structures in the flow educed using SPOD; in fact, if the non-linear terms in the NS equations expanded about the mean flow are uncorrelated in space, SPOD and resolvent response modes are identical. This provides a rigorous explanation for the success of resolvent analysis in predicting coherent structures in various turbulent flows [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}.
